Implementation of Optically Stimulated Luminescent Detectors in the Clinical Setting

Purpose: To perform experiments to determine how Optically Stimulated Luminescent Detectors (OSLDs) can be used for in vivo dosimetry in the clinical environment. For clinical use, OSLDs should have stable, reproducible behavior in measuring dose and be easy to use.

Methods: OSLDs were placed in solid water at dmax, with 12cm of solid water below for backscatter, and were irradiated with a TG51 calibrated linac at 10MV, 100SSD and with a 10x10 cm2 field. The OSLDs were of the Nanodot type from Landauer; the Landauer microStar reader was used to measure photomultiplier counts. No modifications were made to the reader, e.g., use of special filters. OSLDs were irradiated to a variety of dose levels which could be encountered in the clinic, as well as levels of 200Gy or more. OSLDs were bleached after each irradiation with a compact fluorescent light source.

Results: Without preirradiation to relatively high doses, OSLDs displayed non-stabilized supralinear behavior in plots of counts versus dose; dosing histories where cumulative dose is acquired solely in amounts comparable to clinical levels, e.g., <10Gy per irradiation, do not yield useful detectors; the counts versus dose curve continues to change significantly with acquired cumulative irradiation until cumulative dose reaches 250Gy or more. However, irradiation of OSLDs to as little as 200Gy before use yields stable detectors that followed supralinear behavior characterized with a quadratic polynomial fit. Pre-irradiation of 1kGy or more, as reported by Jursinic*, is not needed to yield stable detector performance.

Conclusion: Nanodot OSLDs can be used in a clinical setting after receiving one shot preirradiations of ~200Gy. Dose measuring performance is stable after the preirradiation treatment. One shot irradiations of 1kGy or more are not needed to obtain stable counts versus dose performance.* P. Jursinic, Med. Phys. 37, p. 132 to 140 (2010)